#include <reg51.h>
sbit LED0=P1^0; // 用sbit 关键字 定义 LED到P1.0端口
void Delay(unsigned int t); //函数声明
void main (void)
{
unsigned int CYCLE=600,PWM_LOW=0; //定义周期并赋值
P1=0xFF; //关闭所有流水灯
while (1) //主循环
{
LED0=1;
Delay(60000);
for(PWM_LOW=1;PWM_LOW<CYCLE;PWM_LOW++)
{ //PWM_LOW表示低电平时间，这个循环中低电平时长从1累加到CYCLE（周期）的值，即600次
LED0=0; //点亮LED
Delay(PWM_LOW);//延时长度，600次循环中从1加至599
LED0=1; //熄灭LED
Delay(CYCLE-PWM_LOW);//延时长度，600次循环中从599减至1
}
LED0=0;
for(PWM_LOW=CYCLE-1;PWM_LOW>0;PWM_LOW--)//与逐渐变亮相反的过程
{
LED0=0;
Delay(PWM_LOW);
LED0=1;
Delay(CYCLE-PWM_LOW);
}
}
}
void Delay(unsigned int t) //延时时(t*10)us
{
while(--t);
}
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